Wireless Earplug with Improved Sensitivity and Form Factor

ABSTRACT

An improved wireless communications earplug for use with a magnetic field transmitter. The wireless earplug has a receiver made of a coil of wire on a magnetic bobbin, mounted in close proximity or in contact with a magnetic case of a speaker. The magnetic case of the speaker serves to increase the magnetic flux through the receiver and improves the efficiency of the earplug. The speaker is acoustically coupled to an eartip, and the earplug may be molded into a custom earplug body.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending application Ser. No.12/832,363, filed Jul. 8, 2010, entitled “Wireless Earplug with ImprovedSensitivity and Form Factor”, published as publication number2010/0296667, which claimed benefit of Provisional Application Number61/224,531, filed Jul. 10, 2009, entitled “Wireless Earplug withImproved Sensitivity and Form Factor”, and which was acontinuation-in-part of copending U.S. application Ser. No. 11/837,129,entitled “Wireless Communications Headset System Employing a LoopTransmitter That Fits Around the Pinna”, filed Aug. 10, 2007, andpublished on Feb. 12, 2009, as US2009/0041285, which claimed the benefitof Provisional Application No. 60/824,091, filed Aug. 31, 2006, entitled“Wireless Communications System Employing a Loop Transmitter That FitsAround The Pinna”. The aforementioned applications are herebyincorporated herein by reference.

ACKNOWLEDGMENT OF GOVERNMENT SUPPORT

This invention was made with Government support under SBIR contractN68335-06-C-0372, awarded by the US Navy. The government has certainrights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to the field of communications earplugs. Moreparticularly, the invention pertains to a wireless earplug for use witha magnetic induction communications system.

2. Description of Related Art

It is well documented in literature that the use of double hearingprotection (earmuff and earplug) is superior in providing noiseattenuation compared to using only one hearing protection device alone.Often communications are also necessary, and thus, a communicationsearplug is used.

U.S. Pat. No. 4,972,491, “Ear-Mic Headseat/Eardefender” shows such anarrangement where earplugs within earmuffs/headset are hard-wired to aheadset cord. This is discussed in the June, 2000, issue of the Journalof the Audio Engineering Society in an article entitled “Development ofthe Wireless Communications Earplug for Application in Military Aviation(Van Wijngaarden et al, J. Audio Eng. Soc., Vol. 48, No.6, pp. 553-558).

The problem with typical communications earplugs is that they employwires to provide the communications signal, and the problems with usingwires are manifold.

Inductive coupling for communications is known to the art. For example,see U.S. Pat. No. 2,268,665, “Method and Arrangement for TransferringTelephone Conversations to Other Electrical Devices” which is a cradlefor telephone handset which picks up sound by inductance, or U.S. Pat.No. 3,322,897, “Coil Pick-up and Tube Recorder System” which usescircular loop pickup around handset earpiece to pick up telephonesignals for a recorder.

Inductive coupling is commonly used between a telephone handset and ahearing aid. This application is often referred to as a “T-coil”. Forexamples, see U.S. Pat. No. 2,530,621, “Wearable Hearing Aid withInductive Pick-Up for Telephone Reception”, or U.S. Pat. No. 5,796,821,“Hearing aid telephone interconnect system”.

U.S. Pat. No. 3,125,646, “Electromagnetically Coupled Hearing Aid”couples an amplified signal from a sound input unit in eyeglasses orheadband to a sound output unit in user's ear.

U.S. Pat. No. 5,420,930, “Hearing aid device” uses a receiver assemblyhaving a flexible coil shape worn in the outer portion of the auditorycanal with a small transducer that extends into the auditory canal, anda transmitter assembly. The receiver is driven by magnetic inductionfrom the transmitter assembly positioned a few inches away, as in a neckpendant. Similarly, in U.S. Pat. No. 6,208,740, “Stereophonic magneticinduction sound system” the user wears a necklace with transmitter whichtransmits sound inductively to active receiver units in ears.

US Published Patent Application 2004/151,334, “Actuator for an activenoise control system” is an in-ear transducer for use in ANR systemswith several embodiments, all including permanent magnets, diaphragmsand voice coils.

US Published Patent Application 2005/18,859, “Optically Driven AudioSystem” shows an alternate system of earmuffs/in-ear earplug usingoptical transmission from transmitters to active receivers.

SUMMARY OF THE INVENTION

The invention provides an improved wireless communications earplug foruse with a magnetic field transmitter comprising a loop of wiresurrounding the pinna of a user's ear or other transmitters thatgenerate a magnetic field. The wireless earplug has a receiver made of acoil of wire on a magnetic bobbin, mounted in close proximity or incontact with a magnetic case of a speaker. The magnetic case of thespeaker serves to increase the magnetic flux through the receiver andimproves the efficiency of the earplug. The speaker is acousticallycoupled to an eartip, and the earplug may be molded into a customearplug body.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a transmitter coil mounted behind an ear cushion and awireless communications earplug.

FIG. 2 shows a schematic of the relationship between transmitter andreceiver coils.

FIG. 3 shows a speaker located within receiver coils.

FIG. 4 shows an example of a wireless earplug using a loop receiver.

FIG. 5 shows the earplug of FIG. 4 with the lid and eartip removed.

FIG. 6 shows elements of a wireless earplug, with a dime for scale.

FIG. 7 shows a wireless earplug with speaker and coil installed.

FIG. 8 shows a wireless earplug shell with flange eartip attached.

FIG. 9 shows a wireless earplug in an artificial ear.

FIG. 10 shows the view of FIG. 7 with the back of the earshell removed.

FIG. 11 shows speaker and receiver orientation, off-center.

FIG. 12 shows speaker and receiver orientation, on-center.

FIG. 13 shows a molded silicone earplug and wireless earplug.

FIG. 14 shows a molded earplug with embedded wireless earplug shell.

DETAILED DESCRIPTION OF THE INVENTION

A wireless magnetic induction communications system was previouslydescribed in co-pending patent application entitled “WirelessCommunications Headset System Employing a Loop Transmitter That FitsAround the Pinna, U.S. Ser. No. 11/837,129, filed Aug. 10, 2007, andpublished on Feb. 12, 2009, as US2009/0041285. That application,incorporated herein by reference, describes a wireless magneticinduction communications system. Wireless earplugs are advantageouscompared to wired earplugs because there is no communications cablewhich can be snagged on objects during use which can rip the earplug outof the ear causing pain and loss of communications. Communications wiresare cumbersome and also create acoustic leaks when the cables passbetween the skin and an earmuff ear cushion. In the present invention abattery is preferably not used to power the wireless earplug, andtherefore communications will not be interrupted due to battery failure.In addition, small batteries are relatively expensive.

If acoustic dampers are used in the sound delivery duct, debris isprevented from getting into the earplug, including fluids at lowerpressures. The invention does not require active electronics that canfail in the field and be damaged by electro-static discharge; hence, theinvention is very reliable and robust.

As shown in FIG. 1, an embodiment of a magnetic induction wirelesscommunications system includes a loop transmitter and a loop or coilreceiver. The loop transmitter is used to generate a magnetic field,while the loop receiver converts the magnetic field to a voltage whichis input to a speaker in a communications earplug. Novel features of thesystem are that it operates at audio frequencies, generates essentiallyno radio frequency interference, is compact, and requires no battery inthe communications earplug.

A transmitter coil 1 mounted behind an ear cushion 4 and a wirelesscommunications earplug 35 (with back cover removed) is shown in FIG. 1.The earplug cover is removed exposing the receiver coil 21 and speaker23 locations. The transmitter is located behind the ear cushion 4 of aheadset (headset not shown). The ear cushion 4 and transmitter 1 bothfit around the pinna 50 of an ear (here shown as artificial ear 51, amodel generally in the size and shape of a human ear, of a type oftenused in acoustical testing laboratories).

As shown schematically in FIG. 2, voltage V_(in) applied to thetransmitter coil generates current i_(in) which generates a field ofmagnetic flux, and the field is converted to a voltage V_(out) by areceiver coil. The receiver coil voltage, V_(out), is input to a speaker(not shown in the figure). In this way, audio-frequency signals can betransmitted to a speaker in a wireless manner without the use of abattery in the communications earplug.

As shown in FIG. 3, in the U.S. Ser. No. 11/837,129 invention, thereceiver coil wire 21 is wrapped around the earplug communicationsspeaker 23. This geometry was used to minimize the physical volume ofthe device. If the speaker is made of magnetic material, which istypically the case with hearing aid speakers, the speaker acts as amagnetic core which focuses the magnetic field through the coils andresults in significantly improved sensitivity.

In FIG. 4, an example of a wireless earplug 40 is seen with a rubberflange eartip 35 (other types of eartips, such as foam, may be used).

In FIG. 5, the lid 46 of earplug 40 shown in FIG. 4 has been removed toshow the components of the wireless communications earplug. A loopreceiver 45 comprises a coil 21 wrapped around a speaker 23. Soundgenerated by the speaker 23 is routed through a nipple 44, and thus intothe eartip 35. The eartip 35 has a channel through its center thatprovides an acoustical path which allows sound to be transmitted fromspeaker 23 to the user's ear canal.

The basic elements of an improved wireless earplug of the presentinvention are shown in FIG. 6.

From left to right are an eartip 60, speaker 61, a receiver 67comprising a coil 62 wrapped around a magnetic material bobbin 63, andearshell 75. The speaker 61 has a sound port 69 where sound generated bythe speaker 61 exits the speaker 61. The sound port 69 is acousticallycoupled to a nipple 65 of the earshell 75. A dime is included in FIGS. 6through 13 to indicate size, although it will be understood that thesize of the components may be varied within the teachings of theinvention.

The eartip 60 shown is a rubber triple-flange type; however, there aremany other types of eartips commonly used for communications earplugsthat could be employed, such as single-flange rubber, foam, andcustom-fit types. The eartip 60 is mounted to the nipple 65 of theearshell 75 to provide a full or partial seal between the nipple 65 andan ear canal to generally prevent ambient noise from entering the earcanal. The eartip 60 has a sound delivery tube or channel 66 runningthrough its center to allow the acoustic signal from the speaker 61 tobe delivered to the ear canal to provide communications.

In FIG. 7 the speaker 61 and receiver 67 are installed in the earplug 64and the back 68 of the earshell 75 is attached. The earplug 64 with arubber flange eartip 60 attached is shown in FIG. 8. As stated earlier,many other communications eartips can be attached to the communicationsearplug.

The communications earplug 64 as it fits in an artificial ear 51 can beseen in FIG. 9. The eartip 60 and nipple fit into the ear canal, whilethe rest of the earplug generally forms an L shape geometry within theconcha 94. One can see that the L-shape of the earplug 64 allows it tofit under the tragus 93 while the receiving coil 62 fits in the concha94 area without causing pressure points in the ear. This design resultsin superior comfort compared to design geometries that contact thetragus 93 and/or concha 94 side wall. The L-shape also prevents theearplug from being inserted too deeply and facilitates correct receiverorientation relative to the transmitter coil, not shown in this figure,which can surround the pinna 50 in the system shown in FIG. 1 or can beotherwise configured and located so as to generate a field of magneticflux through the receiver 67.

In FIG. 10 the speaker 61 and receiver coil 62 are installed in theearplug 64. The back of the earshell 75 has been removed so that thespeaker 61 and coil 62 and bobbin 63 of the receiver 67 can be seen.Although not seen in the photo, the wires from the receiver 67 coil 62should be electrically connected to the speaker 61. As stated earlier,the magnetic field through the coil 62 generates a voltage which is usedto drive the speaker 61.

The receiver 67 is installed so that it is in close proximity to thespeaker 61, and makes physical contact with the speaker 61 in thepreferred embodiment. A very small gap (less than 0.005 in) between thereceiver 67 and speaker 61 won't affect the sensitivity of thecommunications earplug appreciably, but larger gaps will. The speaker 61casing, when made of magnetic material, acts to increase the flux linesthrough the coil 62 and increases the effective inductance of the coil62. The most effective orientation of the speaker 61 relative to themagnetic bobbin 63 is one that will help to increase the lines ofmagnetic flux through the magnetic bobbin 63.

FIG. 11 shows the speaker 61 and receiver 67 coil 62 orientation whenmounted in the earshell (not shown in this figure). The coil 62 wiresare electrically connected to the speaker 61 to provide thecommunications electrical signal. As previously discussed, the receiver67 employs a coil 62 of wire wrapped around a magnetic bobbin 63.Transformer wire has been found to work well for the coil 62, andmagnetic ceramic material has been found to work well for the bobbin 63.

The speaker 61 casing is preferably at least partially made of amagnetic metal material. If the speaker casing as manufactured is notmade of a magnetic metal material, it can be placed inside a smallenclosure made of magnetic metal material, creating a magnetic metalspeaker casing. The top surface 101 of the speaker 61 casing that is inclose proximity to the receiver 67, should be made of magnetic material.Additionally, side surfaces 102 of the speaker 61 casing, front endsurface 104, and back end surface 105 should be made of magneticmaterial to the extent possible. The top 101 sides 102 and ends 104 and105 provide a low-reluctance path for the magnetic field flux lines 108that pass through the receiver 67, which improves the efficiency of theearplug. It is less important that a bottom surface 103 of the speaker61 casing be made of magnetic material. If an enclosure is used aroundthe speaker 61, a hole needs to be provided for the sound port 69 of thespeaker where sound exits the speaker 61. The speaker 61 orientationrelative to the receiver 67 can change, but the orientation of thespeaker 61 with receiver 67 and speaker 61 surfaces should be chosen toensure that flux lines are directed through the receiver 67 and notaround the receiver 67 in a shunting manner.

The amount of copper used for the coil 62 should be maximized whilekeeping the overall size of the device within reasonable limits to fitin an ear. The size of the wire and number of turns in the coil 62 whenwound on magnetic bobbin 63 and mounted upon speaker 61 are also chosento generally match the electrical impedance of the speaker 61 to achievehigh efficiency. A ceramic magnetic bobbin 63 wound with a coil 62comprising 500 turns of 40 AWG transformer wire yields a resistance of22 ohms and inductance of 6.8 mH, which has been found to work well witha 22 ohm 3.0 mH hearing aid speaker made by Knowles of Itasca, Ill. Thespeaker 61 used in this invention is small, efficient, and employs acasing made of magnetic material. When placed in contact with thespeaker 61, the effective inductance of this example receiver coil 62increases to 8.4 mH.

Preferably, the magnetic receiver 67 and bobbin 63 should be as close aspossible to the speaker 61. If the receiver 67 bobbin 63 and speaker 61are spaced with only a 0.03 inch gap apart, a loss of 2 dB insensitivity results, compared to when the bobbin 63 and speaker 61 aretouching, and the system requires 58% more power for the same outputlevel. The loss in sensitivity becomes 3.5 dB when the speaker 61 andreceiver 67 are far apart.

The sensitivity of the earplug of the present invention is approximately5 dB higher than the design of prior application Ser. No. 11/837,129shown in FIG. 5 and requires 68% less power for the same output level.Due to the improvement in sensitivity of the wireless system, thetransmitter can be located a further distance (approximately 0.75 in)away from the communications earplug with the same sensitivity. Inaddition, the new L-shaped design geometry orientation results in abetter physical fit in the human ear.

FIG. 12 shows another configuration of the speaker 61 and receiver 67.In this configuration, the receiver 67 is centered over the speaker 61.The resulting sensitivity is slightly higher than in the configurationof FIG. 11. As before, it is preferable that the receiver 67 bobbin 63and speaker 61 casing are as close as possible, preferably touching. Thesound port 69 of the speaker 61 is pointing to the left in the previousphotos; however, other designs with the sound port 69 facing otherdirections will work as well. In addition, the speaker 61 orientationmay change; however, the speaker 61 and receiver 67 should be located asclose as possible to each other and be oriented to draw the lines ofmagnetic flux through the bobbin 63 to yield the highest efficiency.

An element that can be added to the communications earplug 64 includesan acoustic damping element located in the earshell nipple 65 eartip 60,sound port 69 or other location in the acoustic path. Acoustic dampingelements are often used in communications earplugs and hearing aids.They dampen resonances in the acoustic response and are oftenimplemented using screen material or foam. These dampers also preventearwax and debris from entering the earshell and damaging the speaker61.

Electronic equalization can also be used in between the receiver coil 62and speaker 61 to shape the frequency response of the earplug 64. Forexample, as shown in FIG. 3, a capacitor 30 can be installed in parallelwith the coil 21 and speaker terminals 31 to boost the frequencyresponse at select frequencies, such as the region around 3 kHz. A 1 μFcapacitor wired in parallel with the receiver and speaker is effectivefor boosting the 3 kHz region when using the receiver described above.Other passive equalization networks may be used to tailor the responseof the system.

The new geometry enables the earplug to be used alone as a generallyuniversal-fitting earplug, or embedded in a custom-molded earplug body.FIG. 13 shows a custom-molded earplug body 70 and the wireless earplug64 of the invention, with a dime for size reference. The custom-moldedearplug body 70 may be made of silicone, vinyl, acrylic and othermaterials that range from soft to hard.

FIG. 14 shows the wireless earshell 75 as it could be embedded in thecustom-molded earplug body 70. The receiver 67 stands proud of the body70, but will not contact any part of the ear because it extends in theconcha region of the ear. The rest of the earshell 64 is fully embeddedwithin the custom-molded earplug body 70.

When constructing this custom-molded earplug body 70, one needs toremove a region 71 within the portion 72 of the body 70 that extendsinto the ear canal to provide a sound delivery path. This is commonlydone in a custom-molded communications earplug. The sound delivery path71 must reach the sound port 69 of the speaker 61 so that an acousticpath exists from the speaker 61 to the interior of the user's ear canal.

The earshell 75 nipple 65 may be shortened, and/or the angle of thenipple 65 to the custom-molded earplug body 70 may be changed for abetter fit. In addition, the nipple 65 may be eliminated and the soundpath 71 through the custom-molded plug body 70 may extend to an openingin the body of the earshell to provide the sound delivery path. Acousticdamping material 73 can be used in the sound delivery path to dampenacoustic peaks in the frequency response.

Accordingly, it is to be understood that the embodiments of theinvention herein described are merely illustrative of the application ofthe principles of the invention. Reference herein to details of theillustrated embodiments is not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe invention.

What is claimed is:
 1. A wireless communications earplug for use with amagnetic field transmitter, comprising: a) a receiver comprising a coilof wire wound upon a bobbin of magnetic material; and b) a speakerhaving a case at least partially made of magnetic material, an acousticoutput and an electrical input coupled to the wire of the receiver;wherein the bobbin of the receiver is mounted in close proximity to thecase of the speaker to increase magnetic flux through the receiver. 2.The earplug of claim 1, further comprising an eartip for insertion intoa user's ear canal, acoustically coupled to the acoustic output of thespeaker.
 3. The earplug of claim 2, in which the earplug furthercomprises a molded earshell having a body encasing at least the speaker,and the eartip forms part of the molded earshell.
 4. The earplug ofclaim 1, in which the bobbin of the receiver is in contact with the caseof the speaker.
 5. The earplug of claim 1, in which the receiver iscentered upon the case of the speaker.
 6. The earplug of claim 1, inwhich the acoustic output of the speaker is adjacent to an end of thespeaker, and the receiver is mounted upon the case of the speaker at anopposite end from the acoustic object, such that the receiver and thespeaker form an L shape.
 7. The earplug of claim 1, further comprisingan acoustic damping element coupled to the acoustic output of thespeaker.
 8. The earplug of claim 1, further comprising an equalizationcircuit coupled to the coil and to the speaker.
 9. A communicationssystem comprising: a) a magnetic field transmitter; b) a receivercomprising a coil of wire wound upon a bobbin of magnetic material; andc) a speaker having a case at least partially made of magnetic material,an acoustic output and an electrical input coupled to the wire of thereceiver; and wherein the bobbin of the receiver is mounted in closeproximity to the case of the speaker to increase magnetic flux throughthe receiver.
 10. The system of claim 9, further comprising d) an eartipfor insertion into a user's ear canal, acoustically coupled to theacoustic output of the speaker.
 11. The system of claim 10, in which theearplug further comprises a molded earshell having a body encasing atleast the speaker, and the eartip forms part of the molded earshell. 12.The system of claim 9, in which the bobbin of the receiver is in contactwith the case of the speaker.
 13. The system of claim 9, in which thereceiver is centered upon the case of the speaker.
 14. The system ofclaim 9, in which the acoustic output of the speaker is adjacent to anend of the speaker, and the receiver is mounted upon the case of thespeaker at an opposite end from the acoustic object, such that thereceiver and the speaker form an L shape.
 15. The system of claim 9,further comprising an acoustic damping element coupled to the acousticoutput of the speaker.
 16. The system of claim 9, further comprising anequalization circuit coupled to the coil and to the speaker.
 17. Thesystem of claim 9, in which the magnetic field transmitter comprises acoil of wire having an open center sized to fit around a pinna of auser's ear.